Pyrolysis reactions in the presence of an alkene

ABSTRACT

Described herein are methods for producing branched alkanes and branched alkenes from the pyrolysis of radical precursors. The branched alkanes and branched alkenes have numerous applications as fuels, platform chemicals, and solvents.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 14/775,949, filed on Sep. 14, 2015, which is a U.S. national phaseapplication under 35 USC 371 of international application numberPCT/IB2014/001595, filed Mar. 14, 2014, which claims priority to U.S.provisional application Ser. No. 61/792,544 filed Mar. 15, 2013. Theseapplications are hereby incorporated by reference in their entiretiesfor all of their teachings.

BACKGROUND

There are increasing social and economic pressures to develop renewableenergy sources as well as renewable and biodegradable industrial andconsumer products and materials. The catalytic conversion of naturalfeedstocks to value-added products has resulted in new approaches andtechnologies whose application spans across the traditional economicsectors. There is a new focus on biorefining, which can be described asthe processing of agricultural and forestry feedstocks capturingincreased value by processing them into multiple products includingplatform chemicals, fuels, and consumer products. The conversion oftallow and other organic oils to biodiesel has been previously studiedin depth. Traditionally, this conversion involves thetrans-esterification of the triglyceride to produce threemethyl-esterified fatty acids and a free glycerol molecule. Thechemical, rheological, and combustion properties of the resulting“biodiesel” have also been extensively investigated. Unfortunately,these methyl-ester based fuels have been shown to be far moresusceptible to oxidation and have lower heating values than thetraditional petroleum based diesel fuels. As a result the traditionalbiodiesels must be blended with existing diesel stock and may also haveto be supplemented with antioxidants to prolong storage life and avoiddeposit formation in tanks, fuel systems, and filters.

If methyl-esterification can be considered a clean controlled reaction,a relatively crude alternative that has been utilized previously inindustry is pyrolysis. Pyrolysis involves the use of a thermal treatmentof an agricultural substrate to produce a liquid fuel product. Mostliterature reports utilize raw unprocessed agricultural commodities toproduce a value-added fuel. Many different approaches to pyrolysis as amechanism of producing a liquid fuel have been reported in theliterature and fall under various regimes including flash, fast, andslow pyrolysis. The pyrolysis of a variety of agricultural productsunder these different regimes has been previously investigated,including castor oil, pine wood, sweet sorghum, and canola. Depending onthe conditions used including the temperature used, residence time, andpurity of substrate the balance of products produced varies betweenvapors, liquids, and residual solids (char).

One of the few studies to look at the pyrolysis of fatty acids insteadof the triglycerides or more complex substrates focused on the pyrolysisof the salt of the fatty acid. The conditions used in the study weresuch that a homogeneous decarboxylation product was not produced.Instead a mixture of hydrocarbon breakdown products was produced and wasnot identified by the authors. In general, the decarboxylation ofcarboxylic acids that do not contain other interacting functional groupsat high temperature and pressure is poorly understood in the literature.Gaining a better fundamental understanding of the chemistry andmethodologies necessary to promote decarboxylation of fatty acids, orcracking reactions to larger smaller alkanes and alkenes, may allow thefuture development of new fuel and solvent technologies. In one aspect,described herein is the thermal treatment of fatty acids under anoxicconditions. Processes of this nature hold the potential to produce ahigher grade fuel than the traditional biodiesels, and yet wouldpotentially produce higher yields of desirable products than pyrolysis.

SUMMARY

Described herein are methods for producing branched alkanes and branchedalkenes from the pyrolysis of radical precursors. The branched alkanesand branched alkenes have numerous applications as fuels, platformchemicals, and solvents. The advantages of the materials, methods, andarticles described herein will be set forth-in part in the descriptionwhich follows, or may be learned by practice of the aspects describedbelow. The advantages described below will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive.

BRIEF DESCRIPTION OF FIGURES

The accompanying Figures, which are incorporated in and constitute apart of this specification, illustrate several aspects described below.

FIG. 1 shows a proposed mechanism for the formation of branched alkenecompounds from the reaction of alkyl radical species with ethylene andpropylene.

FIG. 2 shows a proposed mechanism for the formation alkane branchedcompounds from the reaction of alkyl radical species with ethylene andpropylene.

FIG. 3 shows the alkane (linear, branched, and cyclic) composition ofliquid oleic acid pyrolysis product from pyrolysis reactions conductedat 410° C. for 2 h using nitrogen, ethylene, and propylene.

FIG. 4 shows the alkene (linear, branched, and cyclic) composition ofliquid oleic acid pyrolysis product from pyrolysis reactions conductedat 410° C. for 2 h using nitrogen, ethylene, and propylene.

FIG. 5 shows liquid product yields at different initial headspacepressures under nitrogen and ethylene atmospheres.

FIG. 6 shows GC-FID chromatograms of liquid oleic acid pyrolysis productobtained from reactions under nitrogen (A) and ethylene (B) headspaces.Reactions were carried out at 410° C. for 2 hours.

FIG. 7 shows total branched alkanes and alkenes in liquid product undernitrogen and ethylene atmospheres at different initial headspacepressures.

FIG. 8 shows a GC-FID chromatogram of oleic acid pyrolysis productobtained from reactions conducted at 430° C. for 2 hour under initialpressure of 500 psi using nitrogen and ethylene.

FIG. 9 shows carbon monoxide content in the gas product of nitrogen andethylene headspace at different initial pressures. Bars with the samenumbers above them are not significantly different at the 95% confidencelevel between the headspace gases at the same pressure. Bars with thesame letters are not significantly different at the 95% confidence levelfor the same headspace gas at different initial headspace pressures.

FIG. 10 shows carbon dioxide content in the gas product of nitrogen andethylene headspace at different initial pressures. Bars with the samenumbers above them are not significantly different at the 95% confidencelevel between the headspace gases at the same pressure. Bars with thesame letters are not significantly different at the 95% confidence levelfor the same headspace gas at different initial headspace pressures.

DETAILED DESCRIPTION

Before the present materials, articles, and/or methods are disclosed anddescribed, it is to be understood that the aspects described below arenot limited to specific compounds, synthetic methods, or uses as suchmay, of course, vary. It is also to be understood that the terminologyused herein is for the purpose of describing particular aspects only andis not intended to be limiting.

In this specification and in the claims that follow, reference will bemade to a number of terms that shall be defined to have the followingmeanings:

Throughout this specification, unless the context requires otherwise,the word “comprise,” or variations such as “comprises” or “comprising,”will be understood to imply the inclusion of a stated integer or step orgroup of integers or steps but not the exclusion of any other integer orstep or group of integers or steps.

It must be noted that, as used in the specification and the appendedclaims, the singular forms “a,” “an” and “the” include plural referentsunless the context clearly dictates otherwise. Thus, for example,reference to “an oil” includes a single oil or mixtures of two or moreoils.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not.

Described herein are methods for producing branched alkanes and branchedalkenes from a radical precursor. In one aspect, the method involvesheating a source having one or more radical precursors in the presenceof one or more alkenes. The phrase “a source of the radical precursor”is defined herein as any material that contains carbon-based moleculesthat can be converted to free radicals upon pyrolysis in the presence ofan alkene. In one aspect, the source of the radical precursor can be aheavy oil, a biomass feedstock, or a fatty acid resource.

The term “heavy oil” as defined herein is any source or form of viscousoil. For example, a source of heavy oil includes tar sand. Tar sand,also referred to as oil sand or bituminous sand, is a combination ofclay, sand, water, and bitumen.

The term “biomass feedstock” as defined herein refers to material from abiological source, such as, for example, a plant, that can be convertedinto a source of energy. In some aspects, the energy source isrenewable. In one aspect, the biomass feedstock is a lignocellulosicmaterial. “Lignocellulosic material” is any dry material from a plantand includes, at a minimum, carbohydrates such as cellulose andhemicellulose and/or polyphenolic compounds such as lignin.Lignocellulosic material may be obtained from agricultural residues suchas, for example, corn stover or wheat straw; from byproducts of wood orpaper processing such as, for example, sawdust or paper mill discards;from crops dedicated to biomass production; from municipal waste suchas, for example, paper; or a combination thereof.

The term “fatty acid resource” as defined herein is any source of fattyacid. The fatty acid can include the free fatty acid or thecorresponding salt thereof. The term “free fatty acid” is referred toherein as the acid form of the fatty acid (i.e., terminal —COOH group)and not the corresponding salt. Alternatively, the fatty acid resourcecan include precursors to fatty acids. For example, the fatty acidprecursor can be a lipid, a triglyceride, a diglyceride or amonoglyceride.

Examples of fatty acid resources include, but are not limited to,vegetable oil, animal fats, lipids derived from biosolids, spent cookingoil, lipids, phospholipids, soapstock, or other sources oftriglycerides, diglycerides or monoglycerides. In one aspect, thevegetable oil comprises corn oil, cottonseed oil, canola oil, rapeseedoil, olive oil, palm oil, peanut oil, ground nut oil, safflower oil,sesame oil, soybean oil, sunflower oil, algae oil, almond oil, apricotoil, argan oil, avocado oil, ben oil, cashew oil, castor oil, grape seedoil, hazelnut oil, hemp seed oil, linseed oil, mustard oil neem oil,palm kernel oil, pumpkin seed oil, tall oil, rice bran oil, walnut oil,a combination thereof. In another aspect, the animal fat comprisesblubber, cod liver oil, ghee, lard, tallow, derivatives thereof (e.g.,yellow grease, used cooking oil, etc.), or a combination thereof.

It is contemplated that the fatty acid resource can be further purifiedprior to subsequent processing. For example, the fatty acid resource canbe distilled or extracted to remove any undesirable impurities. In thealternative, the fatty acid resource can be used as-is. The source ofthe fatty acid resource will determine if any pre-purification steps arerequired. The fatty acid resource can subsequently be pyrolyzed in thepresence of an alkene using the techniques described below.

In certain aspects, the fatty acid resource can be further processedprior to pyrolysis in order to convert certain components present in thefatty acid resource into other species. In one aspect, the methodcomprises:

-   a. separating one or more fatty acids from a fatty acid resource;    and-   b. heating the fatty acid in the presence of one or more alkenes to    produce a fuel or solvent including one or more alkanes, alkenes, or    a mixture thereof.

In one aspect, separation step (a) involves removing or isolating one ormore fatty acids from the fatty acid resource. A number of differenttechniques are known in the art for the isolation and purification offatty acids. For example, U.S. Pat. No. 5,917,501 discloses a processfor isolating fatty acids. The process involves hydrolyzing a naturallyoccurring lipid mixture containing phospholipids, triglycerides, andsterols to form a two-phase product containing a fatty acid phasecomprised of fatty acids and sterols, and an aqueous phase comprised ofwater, glycerol, and glycerol phosphoric acid esters. The aqueous phaseis separated from the fatty acid phase and the crude fatty acid phase isheated to convert the free sterols to fatty acid sterol esters. The freefatty acids are distilled from the fatty acid sterol esters to yieldpurified fatty acids, which are free of cholesterol and other sterols,and phosphorous compounds. In other aspects, the fatty acid resource isexposed to acid in order to hydrolyze a fatty acid precursor present inthe fatty acid resource to produce the corresponding free fatty acid.For example, vegetable oils are rich in triglycerides, which upon acidhydrolysis, produce the free fatty acid and glycerol.

In certain aspects, after the separation step, it can be desirable toproduce a pure or substantially pure form of the fatty acid. The phrase“substantially pure” as used herein is defined as greater than 90% byweight fatty acid content. The presence of impurities can adverselyaffect the final composition of the fuel or solvent. For example, ifsulfur, oxygen, or nitrogen compounds are present in the fatty acidprior to step (b), undesirable product characteristics result includinghigh sulfur or nitrogen emissions during combustion or side-reactionsmay occur during step (b) such as the formation of undesirable aromaticcompounds.

The nature of the fatty acid will vary depending upon the fatty acidresource. The fatty acid can be a saturated fatty acid, an unsaturatedfatty acid, or a combination thereof. Examples of fatty acids include,but are not limited to, butyric acid, lauric acid, myristic acid,palmitic acid, stearic acid, arachidic acid, alpha-linolenic acid,docosahexaenoic acid, eicosapentaenoic acid, linoleic acid, arachidonicacid, oleic acid, erucic acid, a naturally derived fatty acid from aplant or animal source, or a combination thereof. The fatty acid canalso be a mixture of free fatty acids.

The source of the radical precursor is heated in the presence of one ormore alkenes to produce a branched alkane, a branched alkene, or acombination thereof. In general, the source of the radical precursor isintroduced into a pyrolysis reactor, which is a closed vessel that cansustain high internal pressures and temperatures. In one aspect, themicroreactors disclosed in U.S. Pat. No. 8,067,653, which areincorporated by reference, can be used herein to conduct the pyrolysisstep.

After the source of the radical precursor has been introduced into thepyrolysis reactor, the system is purged with an inert gas such as, forexample, nitrogen or argon. Next, an alkene is introduced into thepyrolysis reactor. The term “alkene” is an organic molecule having onecarbon-carbon double bond. In one aspect, the alkene is a linear orbranched molecule composed solely of carbon and hydrogen. The alkene canbe gas or liquid at ambient temperature. In another aspect, the alkeneis ethylene, propylene, butene or isomers thereof (e.g., isobutene) or amixture thereof.

The amount of alkene that is introduced into the pyrolysis reactor canvary. In certain aspects, a molar excess of alkene relative to thesource of the radical precursor can be employed. For example, the molarratio of fatty acid resource to alkene is from 1:1 to 1:5, 1:1 to 1:4,1:1 to 1:3, or 1:1 to 1:2, where the moles of gas are calculated usingvan der Waal's equation of state for real gases. In other aspects, therecan be a substantially higher amount of the source of the radicalprecursor resource relative to alkene. Thus, depending upon processconditions and reaction kinetics, the relative amount of alkene andsource of the radical precursor can be modified accordingly.

Once the pyrolysis reactor has been charged with the source of theradical precursor resource and alkene, the reactor is heated internallyin order to convert the radical precursor to the branched alkane orbranched alkene. The temperature of the heating step can vary amongstdifferent parameters. In one aspect, the temperature of the heating stepis from 220° C. to 650° C., 300° C. to 650° C., 350° C. to 650° C., 350°C. to 600° C., or 250° C. to 500° C. In another aspect, the heating stepis conducted at 450° C.

The duration of the heating step can also vary depending upon the amountof the source of the radical precursor and alkene used and the pressurewithin the pyrolysis reactor. In one aspect, the pressure in thepyrolysis reactor can range from ambient to 2,000 psi, such as, forexample, 130 psi, 200 psi, or 500 psi, and the duration of the heatingstep can be from seconds up to 12 hours. In one aspect, the heating stepis from two seconds up to 8 hours. In another aspect, the heating stepis conducted for 2 hours. In a further aspect, the reaction time andtemperature are selected to maximize fatty acid feed conversion andliquid product yield while minimizing gas, aromatic compounds, andsolids formation.

By varying reaction conditions during the conversion of the source ofthe radical precursor to the branched alkanes and branched alkenes, oneof ordinary skill in the art can produce short or long chainalkanes/alkenes for fuels and solvents. For example, prolonged heatingat elevated temperatures can produce short chain alkanes/alkenes thatcan be useful as fuels. Alternatively, long chain alkanes/alkenes can beproduced by one of ordinary skill in the art by reducing the heatingtime and temperature. If short chain alkanes or alkenes are produced,reaction conditions can be controlled such that these products are gases(e.g., methane, propane, butane, etc.) that can be readily removed fromthe reactor.

The methods described herein result in the formation of branched alkanesand alkenes. Not wishing to be bound by theory, mechanisms for producingbranched alkanes and alkenes are depicted in FIGS. 1 and 2. FIG. 1 showsa possible reaction scheme for the formation of branched alkenecompounds from the reaction of alkyl radical species with ethylene (oralternatively propylene). In one aspect, the formation of branchedcompounds during pyrolysis of a free fatty acid conducted in presence ofethylene is a multi-step process that follows the thermal deoxygenationof the fatty acid. One possible product of fatty acid deoxygenation isthe generic organic compound “a” in reaction (1), where R represents analkyl group. These compounds are known to undergo cracking at 350 to450° C. between 1 to 4 hours described herein to produce radicalslabeled “b” and “c”, respectively. In reaction (2) radical “b” undergoesa molecular rearrangement to yield radical “d”. Reaction (3) showsethylene (labeled as “e”) reacting with radical “c”, which results inthe formation of branched radical “f”.

FIG. 2 shows a possible reaction scheme for the formation of branchedalkane compounds from the reaction of alkyl radical species withethylene (or alternatively propylene). A possible product of fatty aciddeoxygenation and cracking followed by hydrogen migration to the morestable structure (common in liquid phase free radical systems) is thegeneric organic compound “a” in reaction (4) and (5), where R representsan alkyl group. These radical species, formed from alkane cracking at350 to 450° C.) between 1 to 4 hours described herein can react withethylene “b” or propylene “d” to form branched radical alkane species“c” and “e”. All terminal products identified In FIGS. 1 and 2 throughproduct analysis can be terminated through subsequent hydrogenabstraction from other molecules in the liquid phase.

In one aspect, the methods disclosed herein produce a mixture ofproducts including C₆ to C₁₂ l-alkenes, C₆ to C₁₈ internal alkenes, C₆to C₁₉ n-alkanes, aromatics, branched hydrocarbons, cyclic hydrocarbons,C₄ to C₁₈ fatty acids, and additional unidentified products. In thisaspect, use of an alkene headspace gas can increase the proportion ofdesired products such as, for example, branched hydrocarbons.

In fuel formulations, branched-chain alkanes and alkenes are preferredbecause they are less prone to the phenomenon of knocking (due to theirhigh octane number) compared with their straight-chain homologues. Inaddition, branched alkanes and alkenes find widespread industrialapplications as solvents for nonpolar chemical species. Straight-chainalkanes and alkenes are conventionally converted to branched isomers inindustrial processes such as reforming and isomerization in presence ofmetal catalysts. Additionally, the methods described herein do notrequire the addition of supplemental hydrogen (i.e., hydrogen that isadded to the reaction prior to and/or during pyrolysis of the fattyacid). Supplemental hydrogen. However, supplemental hydrogen does notinclude hydrogen that may be produced in situ during the pyrolysis ofthe fatty acid in the presence of the alkene. These techniques alsorequire pure feedstocks. One significant advantage of the methodsdescribed herein is that branched alkanes can be created without usingany catalysts, which reduces capital and operating costs as well asallow the use of relatively impure feedstock compared to conventionalpetroleum-based operations.

As shown below in the Examples, the methods described produce higherconcentrations of branched alkanes and alkenes in the liquid productcompared to the pyrolysis of the same fatty acid under an inertatmosphere.

In another aspect, the use of a decarboxylation catalyst can be used tofacilitate the conversion of the fatty acid to the alkane or alkene.Depending upon the selection of the decarboxylation catalyst, thecatalyst can reduce the heating temperature and time. This is desirablein certain instances, particularly if degradation of the alkane/alkeneor side reactions (e.g., aromatization) are to be avoided. Examples ofdecarboxylation catalysts include, but are not limited to, activatedalumina catalysts. The use of the decarboxylation catalyst is optional;thus, the methods described herein do not require the presence of adecarboxylation catalyst.

The methods described herein can be performed in batch, semi-batch, orcontinuous modes of operation. For example, with respect to thepyrolysis of the free fatty acid, a continuous reactor system withunreacted acid recycle could be employed to enhance the yield ofdesirable alkane/alkene by limiting the duration and exposure of thealkane/alkene in the high temperature reactor. Carbon dioxide and smallhydrocarbon products could be recovered, with the gas phase hydrocarbonsused as fuel for the reactor or other applications. When a continuousreactor system is used, process conditions can be optimized to minimizereaction temperatures and times in order to maximize product yields andcomposition. As the reaction can be adjusted to select for a preferredcarbon chain length (long, short or medium), the technology has thecapability of enriching for a particular product group. From thesegroups, individual chemicals could be recovered, purified, and sold aspure platform chemicals.

The methods described herein provide numerous advantages over currenttechniques for producing renewable biofuels. The methods describedherein produce higher amounts liquid hydrocarbons, which is demonstratedin the Examples. As described above, the methods described herein can beused to produce higher concentrations of branched alkanes and alkenesthat are useful in modern fuel mixtures. The methods utilize renewableresources to create a non-petroleum based sustainable fuel source withlow levels of aromatic compounds.

The hydrocarbons formed herein are chemically much more uniform thanother high temperature processes currently used. For example, the fuelsor solvents produced herein are substantially free of aromaticcompounds, where the term “substantially free” is defined as less than5% by weight aromatic compounds. It is also contemplated that noaromatic compounds are present in the fuels or solvents.

It is anticipated the methods described herein will provide higherproduct yields than other pyrolysis technologies and will produce a fuelmuch more similar to diesel than biodiesel. In one aspect, the liquidproduct yield as a weight percentage of fatty acid feedstock is from 75%to 110%. In another aspect, the liquid product yield as weightpercentage of fatty acid feedstock is from 95 to 110%, or is about 98%or about 107%. The products will not have the problems of biodiesel inthat they will be oxidatively stable and will have pour points similarto conventional diesel fuel.

In one aspect, the elemental composition of the liquid product can bedetermined. In one aspect, the liquid product contains a higherproportion by weight of carbon than the feedstock. In this aspect, thecarbon content of the feedstock can be from 70 to 80% by weight carbon,from 75 to 79% by weight carbon, or can be about 76.7% by weight carbon.Further in this aspect, the carbon content of the liquid product can befrom 80 to 90% by weight carbon, from 83 to 85.5% by weight carbon, orcan be about 84% by weight carbon.

In a further aspect, the liquid product contains a lower proportion byweight of oxygen than the feedstock. In this aspect, the oxygen contentof the feedstock can be from 5 to 15% by weight oxygen, from 8 to 13% byweight oxygen, or can be about 11.3% by weight oxygen. Further in thisaspect, the oxygen content of the liquid product can be less than 5% byweight oxygen, or can be about 2.1%, about 2.8%, about 3.0%, about 3.1%,or about 3.6% by weight oxygen.

In a still further aspect, deoxygenation of the fatty acid occurs duringthe methods disclosed herein. The methods described herein increase therate of decarboxylation of fatty acids when compared to performing thesame pyrolysis reaction under an inert atmosphere (e.g., nitrogen).

In one aspect, deoxygenation rates can increase as initial headspacepressure increases. Carbon dioxide and/or carbon monoxide is releasedduring the methods disclosed herein. Further in this aspect, carbondioxide production can increase as initial headspace pressure increases.In yet another aspect, nitrogen and sulfur content of the feedstock andthe liquid product(s) is below 10 ppm. In this aspect, the feedstock andliquid product are said to be “substantially free” of nitrogen andsulfur.

Finally, the imput costs are expected to be lower using the methodsdescribed herein when compared to competitive, exisiting biodieseltechnologies. In particular, the process does not require ahydrogenation step to produce hydrocarbons, which adds significant costto the process. Moreover, as demonstrated in the Examples, the methodsdescribed herein decaroboxylate the free fatty acid quicker compared toother techniques, which ultimately shortens reaction times and costs.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thematerials, articles, and methods described and claimed herein are madeand evaluated, and are intended to be purely exemplary and are notintended to limit the scope of what the inventors regard as theirinvention. Efforts have been made to ensure accuracy with respect tonumbers (e.g., amounts, temperature, etc.) but some errors anddeviations should be accounted for. Unless indicated otherwise, partsare parts by weight, temperature is in ° C. or is at ambienttemperature, and pressure is at or near atmospheric. There are numerousvariations and combinations of reaction conditions, e.g., componentconcentrations, desired solvents, solvent mixtures, temperatures,pressures and other reaction ranges and conditions that can be used tooptimize the product purity and yield obtained from the describedprocess. Only reasonable and routine experimentation will be required tooptimize such process conditions.

The laboratory methodologies for sample preparation, reactor assemblyand reaction protocols, product handling, analytical procedures forchemical characterization and quantitation described in U.S. Pat. No.8,067,653 B2 issued on Nov. 29, 2011 were used below. Reactiontemperature and time were selected based on previous experiments withthermal cracking of oleic acids (see Asomaning et al., J. Anal. Appl.Pyrolysis, 2014, 105:1-7). Conditions selected for this study maximizedfatty acid feed conversion and liquid product yield while minimizing theformation of gases, aromatic compounds, and solids. Reactions wereconducted by loading the free fatty acid in the microreactor, sealingthe microreactor, and purging the microreactor with free fatty acid withnitrogen. The pressure inside the reactor at the beginning of thepyrolysis reaction is controlled by charging the microreactor with gas.

Table 1 shows that from microreactors loaded with oleic acid andnitrogen and reacted for 2 hours at 410° C., it is possible to recover81.39% of the total initial mass as liquid product. Pyrolysisexperiments conducted in presence of short chain saturated hydrocarbonssuch as ethane, propane do not produce liquid yields that arestatistically different from the control experiment described above. Inthe case of methane, the liquid yield measured was lower than thenitrogen benchmark and measured at approximately 76%. On the other hand,pyrolysis experiment conducted with unsaturated short chain hydrocarbonssuch as ethylene and propylene produced substantially higher liquidyields (approximately 98% and 107% respectively).

TABLE 1 Liquid product yield from pyrolysis of oleic acid (410° C., 2 h)in presence of nitrogen and hydrocarbon gases Headspace Mole RatioLiquid Product Yield Gas (130 psi) (feed:gas)¹ (wt % of oleic acid feed)Nitrogen 1:1.8 81.4 ± 2.6^(a) Ethylene 1:1.9 98.2 ± 0.9  Ethane 1:1.983.0 ± 1.4^(a) Propylene 1:2.0 107.4 ± 2.6  Propane 1:2.0 83.8 ± 1.1^(a)Methane 1:1.8 76.7 ± 1.1  ¹Moles of gas calculated using thePeng-Robinson equation of state. ^(a)Values with the same superscriptletters are not significantly different at the 95% confidence level.

Chemical characterization of the pyrolysis liquid product by GC-MS andGC-FID confirmed the liquid yield data described above and showed thathigher concentration of alkanes and alkenes can be obtained by reactingoleic acid with unsaturated short chain hydrocarbons compared to inertgases.

FIGS. 3 and 4 show that, with the exception of alkanes with carbonnumber 14, reacting free fatty acids in presence of ethylene yieldssystematically higher concentrations of both alkanes and alkenes. FIG. 5shows that these higher concentrations of alkanes and alkenes resultwith ethylene headspace gas, regardless of the initial headspace gaspressure.

Liquid product characterization by GC-MS and GC-FID techniques revealedthat fatty acids reacted with unsaturated short chain hydrocarbonsproduced a higher concentration of branched alkanes in the liquidproduct compared to the same reactions conducted in inert gasatmosphere. FIG. 6 shows a portion of two typical GC-FID chromatogramsfor liquid samples of oleic acid pyrolysis product obtained fromreactions under nitrogen and ethylene headspaces respectively. FIG. 6clearly shows the presence of a branched alkane with eight carbon atomsin the case of pyrolysis of oleic acid in presence of ethylene. The samecompound is practically absent in the case of pyrolysis in presence ofnitrogen. FIG. 7 demonstrates that using ethylene as headspace gas leadsto an increased yield of branched alkanes and alkenes and that thisyield increases with initial headspace pressure, while for nitrogen, theyield of branched compounds stays roughly the same regardless of initialheadspace pressure.

A careful analysis of the typical GC-FID chromatograms for the liquidoleic acid pyrolysis product revealed that reactions conducted in thepresence of ethylene result in faster fatty acid deoxygenation comparedto the same reactions conducted in a nitrogen atmosphere. FIG. 8 showsthe typical GC-FID chromatograms of liquid products from the pyrolysisof oleic acid in presence of nitrogen and ethylene, respectively. It isimmediately evident by comparing the peaks of the internal standard withthe peaks adjacent to the stearic acid peak (C18:0) that in the case ofpyrolysis of oleic acid in presence of ethylene, the feedstock isconverted more rapidly compared to pyrolysis under an inert atmosphere.

A water/aqueous fraction was not observed in the liquid product obtainedunder all conditions. This does not imply that water was not produced.Water may not have been observed due to the small feed mass used in thisstudy (1 g). A previous study on a larger sample size demonstrated theproduction of a water/aqueous fraction during the pyrolysis of freefatty acids. Composition of the liquid product produced under variousheadspace gases is provided in Table 2.

TABLE 2 Liquid product composition at an initial pressure of 130 psiunder inert gas and light hydrocarbon gas atmospheres Weight % of liquidproduct Class of Headspace gas compounds Nitrogen Methane Ethane PropaneEthylene Propylene C₆ to C₁₂ l-  3.5 ± 0.2  4.1 ± 0.4  3.4 ± 0.2  3.3 ±0.4  3.8 ± 0.4  4.9 ± 1.5 alkenes C₆ to C₁₈ internal 11.3 ± 0.7 11.7 ±0.9 12.5 ± 0.5 12.6 ± 1.3 11.2 ± 0.2 10.6 ± 1.4 alkenes C₆ to C₁₉ n-23.6 ± 1.9^(a) 23.3 ± 2.5^(a) 22.4 ± 2.6^(a) 23.5 ± 1.1^(a) 23.9 ±0.9^(a) 19.5 ± 0.9^(a) alkanes Aromatics  4.7 ± 0.3^(a)  4.4 ± 0.4^(a) 4.6 ± 0.5^(a)  4.7 ± 0.1^(a)  5.5 ± 0.2^(a)  6.1 ± 0.3^(b) Branched 3.5 ± 0.4^(a)  3.4 ± 0.4^(a)  3.0 ± 0.7^(a)  2.8 ± 0.6^(a)  7.8 ±1.5^(b)  6.9 ± 0.9^(b) hydrocarbons Cyclic  9.8 ± 0.7^(a)  9.2 ± 0.4^(a)10.2 ± 0.5^(a) 10.9 ± 0.7^(a) 10.8 ± 0.3^(a) 11.2 ± 0.4^(a) hydrocarbonsC₄ to C₁₈ fatty 15.5 ± 0.8^(a) 12.6 ± 2.4^(a) 11.7 ± 1.7^(a) 13.8 ±1.3^(a) 10.9 ± 1.9^(b)  9.0 ± 0.2^(b) acids Unreacted feed +  2.1 ± 0.6 2.5 ± 0.8  2.8 ± 1.9  2.5 ± 0.8  1.0 ± 0.3  1.0 ± 0.5 isomersUnidentified 18.5 ± 2.8 17.2 ± 1.8 15.9 ± 0.2 16.0 ± 1.9 18.1 ± 2.9 19.9± 1.8 Unaccounted  8.8 ± 3.4 11.5 ± 4.3 13.6 ± 1.1  9.9 ± 1.9  6.9 ± 2.010.6 ± 3.1 ^(a,b)Values in the same row are not significantly differentfrom a nitrogen atmosphere at the 95% confidence level if they have thesame letters.

These experiments show that the efficiency and economic valueproposition of the conversion of lipids to hydrocarbons using a two-stepapproach (hydrolysis of lipids followed by pyrolysis of fatty acids) canbe improved by conducting the second step in presence of a short chainunsaturated hydrocarbon such as ethylene. When such species are present,the fatty acid feedstock is converted more rapidly, yielding a greaterproportion of liquid product in the valuable gasoline, diesel and jetfuel range. Additionally, the methods described herein result in theformation of branched alkanes and alkenes, which are essential elementsin modern fuel mixtures.

The elemental composition of liquid product was determined using a CarloErba EA1108 elemental analyzer at the Analytical and InstrumentationLaboratory in the Chemistry Department at the University of Alberta.Results are presented in Table 3.

TABLE 3 Elemental composition of liquid product together with oleic acidfeed Element (wt %) Headspace gas Nitro- Sul- (pressure in psi) CarbonHydrogen gen fur Oxygen* Feed 76.7 ± 0.1 12.1 ± 0.0 BDL BDL 11.3 ± 0.1 Nitrogen (130) 83.8 ± 0.2 12.6 ± 0.0 BDL BDL 3.6 ± 0.1 Ethylene (130)83.8 ± 0.2 12.6 ± 0.0 BDL BDL 3.6 ± 0.3 Nitrogen (200) 84.4 ± 0.2 12.2 ±0.1 BDL BDL 3.0 ± 0.3 Ethylene (200) 84.3 ± 0.2 12.6 ± 0.0 BDL BDL 3.1 ±0.1 Nitrogen (500) 84.5 ± 0.3 12.7 ± 0.1 BDL BDL 2.8 ± 0.3 Ethylene(500) 85.1 ± 0.2 12.8 ± 0.0 BDL BDL 2.1 ± 0.1 *Calculated by difference.BDL: below detection limit (10 ppm).

The results presented in Table 3 show that both nitrogen and sulfur werebelow the detection limit of 10 ppm in the feed and, as a consequence,the liquid product also had nitrogen and sulfur content below thedetection limit. Further, the results demonstrate deoxygenation duringthe pyrolysis reaction, irrespective of the headspace gas used.Additionally, the results show an increase in deoxygenation as initialheadspace pressure increases.

As seen in FIGS. 9 and 10, carbon monoxide and carbon dioxide areproduced using both nitrogen and ethylene as headspace gases.

Throughout this application, various publications are referenced. Thedisclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the compounds, compositions and methods described herein.

Various modifications and variations can be made to the materials,methods, and articles described herein. Other aspects of the materials,methods, and articles described herein will be apparent fromconsideration of the specification and practice of the materials,methods, and articles disclosed herein. It is intended that thespecification and examples be considered as exemplary.

What is claimed:
 1. A method for producing a branched alkane, branchedalkene, or a combination thereof from a biomass feedstock comprisingheating the biomass feedstock in the presence of one or more alkenes. 2.The method of claim 1, wherein the alkene is ethylene, propylene, buteneor an isomer thereof, or any combination thereof.
 3. The method of claim1, wherein the biomass feedstock is heated under an atmosphere of alkeneat a pressure of ambient to 2,000 psi.
 4. The method of claim 1, whereinthe heating step is conducted at a temperature from 220° C. to 650° C.5. The method of claim 1, wherein the heating step is conducted at atemperature from 250° C. to 500° C. for two seconds up to 8 hours. 6.The method of claim 1, wherein the heating step is conducted in theabsence of supplemental hydrogen.
 7. The method of claim 1, wherein theheating step is conducted in the absence of a catalyst.
 8. A method forproducing a branched alkane, branched alkene, or a combination thereoffrom a heavy oil comprising heating the heavy oil in the presence of oneor more alkenes.
 9. The method of claim 8, wherein the alkene isethylene, propylene, butene or an isomer thereof, or any combinationthereof.
 10. The method of claim 8, wherein the heavy oil is heatedunder an atmosphere of alkene at a pressure of ambient to 2,000 psi. 11.The method of claim 8, wherein the heating step is conducted at atemperature from 220° C. to 650° C.
 12. The method of claim 8, whereinthe heating step is conducted at a temperature from 250° C. to 500° C.for two seconds up to 8 hours.
 13. The method of claim 8, wherein theheating step is conducted in the absence of supplemental hydrogen. 14.The method of claim 8, wherein the heating step is conducted in theabsence of a catalyst.
 15. A branched alkene, a branched alkane, or acombination thereof produced by the method of claim
 1. 16. A branchedalkene, a branched alkane, or a combination thereof produced by themethod of claim 8.